KB stands for kilobyte, while MB is short for megabyte. KB and MB are units of measurement, much like miles and inches. The only difference is that KB and MB are a unit of information.
Base Two vs. Base Ten
There are two different systems you can use when calculating KB and MB. The International System of Units (SI) uses the Base 10 system, while the binary system definition of bytes refers to the Base 2 system.
The Base 10 system is usually used to calculate data transfer speeds, as well as the size of storage systems. The Base 2 system is still used in Microsoft Windows.
More On KB
KB uses the prefix "-kilo." A KB is defined differently depending on which calculation system you are using.
In the Base 10 system, 1KB equals 1000 bytes. However, if you're using the Base 2 system, 1KB is equivalent to 1024 bytes.
KB typically make up smaller files like text documents.
More On MB
MB is the bigger of the two measurements and uses the prefix "-mega." The definition of an MB also differs when you use different systems.
1MB equals 1,000,000 bytes in the Base 10 system. When you use the Base 2 system, 1MB is defined as 1,048,576 bytes.
The size of larger files like long documents, photos, and videos are expressed in MB.